In the manga, Diana appeared significantly earlier than she did in the anime. She appeared during the Black Moon arc, which corresponds with the second storyline of the R season. Like her mother and father, she had the ability to take on human form in times of crisis, though unlike them she retained her tail. Like Chibiusa, her hair was bound in odango on the sides of her head.

She was friendly with Sailor Pluto, due to the fact that Pluto and Chibiusa were friends, and guarded the Space-Time Door for Pluto when she convinced Pluto to join the battle against the Black Moon Clan.

Diana was always very polite and formal, and referred to Usagi and Mamoru as "Serenity-sama" and "Endymion-sama" ("sama" (さま; "様" in kanji) is a non-gender-specific suffix to people's names for showing respect).